How often does Last-Modified change?

Question

PHP

Helped one person with the question Why do search engines not see the full title?
I advised him to look towards Last-Modified,
but I don’t know if he wrote the code correctly so that the date does not change with each generation, but only when the content on the page actually changes, can you inspect the code that he provided on Smarty:

$LastModified_unix = strtotime(date("D, d M Y H:i:s", filectime($_SERVER['SCRIPT_FILENAME']))); 
$LastModified = gmdate("D, d M Y H:i:s \G\M\T", $LastModified_unix); 
$IfModifiedSince = false; if (isset($_ENV['HTTP_IF_MODIFIED_SINCE']))   
$IfModifiedSince = strtotime(substr ($_ENV['HTTP_IF_MODIFIED_SINCE'], 5));
if (isset($_SERVER['HTTP_IF_MODIFIED_SINCE']))    
$IfModifiedSince = strtotime(substr ($_SERVER['HTTP_IF_MODIFIED_SINCE'], 5));
if ($IfModifiedSince && $IfModifiedSince >= $LastModified_unix) {    
header($_SERVER['SERVER_PROTOCOL'] . ' 304 Not Modified');    
exit; } 
header('Last-Modified: '. $LastModified);

Thanks in advance!

Answer 1

filectime($_SERVER['SCRIPT_FILENAME'])
You're reading the modification date of a file, not a database entry or something. You need to understand which elements in the content area can change and take their modification date.
For a static page - the maximum modification date from all text blocks
For a catalog - the maximum modification date from all elements (or we fix it for the catalog itself)
For a filter - always current
For an element - the date the element was modified